At a special AgSTAR seminar held at World Dairy Expo in Madison, Wisconsin, a number of dairy producers and anaerobic digester operators came together to speak openly about their systems by responding to audience questions.
Q. What was your biggest incentive to install a digester?
Lee Jensen of Five Star Dairy in Elk Mound, Wisconsin, said he was able to install a complete mix digester for his 1,000-cow dairy at very little cost.
In a “guinea pig deal,” he partnered with a digester company and power cooperative to install one of the first dairy farm digesters in the state. Since then, he’s found many benefits to the digester, including public perception.
Public education and awareness was the reason why John De Jonge put in a small digester at Bakerview EcoDairy in Abbotsford, British Columbia. Another incentive for him was to see if a 50-cow farm could successfully own and operate a digester.
Having a consistent, reliable bedding source was another reason producers cited for installing a digester on the dairy.
That was one of the driving reasons for John Vrieze of Baldwin Dairy in Emerald, Wisconsin. His first digester, a mixed plug-flow unit, was set up to clean and compress biogas into commercial-grade natural gas. After the market price fell, it was no longer an economical option and now the digester is used primarily to make bedding for the dairy. A second digester of his makes bedding as well as generates heat for a 27,000-square-foot greenhouse.
For Vrieze the installation of a digester goes beyond the farm. “I’m glad we have the digesters,” he said. “Talking to my kids and grandkids, I can say I’m doing something different for their future.”
Q. How do you manage biosolids for bedding?
On De Jonge’s smaller dairy, he uses an automated conveyor system to move the solids from the screwpress into the barn. Employees pull the solids off the conveyor and onto the mattresses.
Both Jensen and Vrieze use a blower to apply solids on top of mattresses in some of their barns nearly every day. They said the blower aids in killing bacteria through oxygenation and exposure to a cooler temperature.
Each of them also has at least one barn with deep beds. Jensen beds that barn three times a week. At Vrieze’s dairy, the back 18 inches of the deep beds are manually dug down 6 to 10 inches and removed every three months.
Mike Geerlings of Scenic View Dairy in Fennville, Michigan, adds solids from his farms’ digesters twice a week using old sand spreaders. The deep bed stalls are raked shallow, just 2 to 3 inches, four or five times a week. Half of the biosolids generated from two farms, nearly 5,000 cows, some heifer and calf housing and a swine operation, are exported off-site to heifer facilities and a greenhouse project.
In Krakow, Wisconsin, Mark Jacobs of Green Valley Dairy finds using biosolids on deep beds to be a challenge. He said he is considering installing a composter after the solid separator to continue to eliminate more of the bacteria in the solids.
Q. Is there a market for biosolids?
According to Geerlings, he does not have an available market in Michigan. “We have tried, but nothing has caught on,” he said.
On the other side of the lake, the Crave Brothers Farm in Waterloo, Wisconsin, has seen success from sales of biosolids. The farm’s two digesters and additional related equipment is actually owned and operated by a third party. That company focused heavily on processing the biosolids to meet the strict quality requirements for steady marketing, Karl Crave explained.
However, unless you are willing to invest time, effort and expertise beyond just coming off the screwpress, Vrieze said you shouldn’t count on sales of solids as a consistent income stream. In his particular situation, he has been able to sell excess solids for $25 a ton in the local area, but for the most part all solids are consumed on the farm.
Still fairly new to operating a digester, De Jonge said there are nurseries nearby and he expects to export 30 to 40 percent of the farm’s solids for $10 a yard.
Q. Did you intend to use other substrates from the start?
“When we went into our system that was part of the plan from day one,” Jensen said. Substrates are brought in solely to generate more energy, but he has also found them to increase the amount of fertilizer for his expanding land base.
Profit was the motivation for Geerlings to use substrates in his digesters. From his experience, he recommends having those feedstocks tested for solids and gas output prior to accepting them. “Even the same product with the same name can vary a lot,” he said.
With an on-farm cheese plant, the Craves intended to add whey to the digesters right from the start. Since then the price of whey increased and they installed an ultrafiltration system, which changed the product that was left for the digesters. Now, Crave said they also supplement with about two loads of a fat product each week.
Due to size limitations of his lagoons, Vrieze never anticipated adding much for liquid substrates. He did say he adds solid materials like old forages and weighbacks to generate additional solids when short on bedding.
Q. Should there be more digesters on dairies in the U.S.?
“Absolutely,” Vrieze said. “I’ve been a fan of renewable energy for 10 to 15 years, whether it’s wind or solar or biogas … Without some regulation or economic incentive, unfortunately, I don’t think we’ll have the same amount of digesters built in Wisconsin as we have the last six or eight years.”
Crave added, “The industry we’re in today no longer has a technical challenge in regards to making biogas or making electricity. It is a policy problem. We have the technology; we have the resources; we have the producers and vendors ready to do it. It’s really a policy change or incentive that is required at this point.”
Q. What would be your dream scenario for support from the public sector?
In Michigan, utility users are subject to a green energy surcharge. Geerlings said he advocates that the surcharge be put towards the cost of interconnection. “The biggest headache we have is hooking up to the grid,” he said. “For example, we bought $275,000 worth of upgrades to the system. We don’t own them and consumers can depreciate them off their books.”
Jensen would like to see more regulations put on the disposal of certain substrates. Digesters have the ability to cleanly dispose of many products, but if it costs those companies a penny a gallon more to get rid of it through a digester versus land application, they won’t.
For Crave, building an incentive based on production would be a solution to keep good systems in operation. “It gives incentive not just to build projects but to operate and maintain them long term,” he said.
Q. What do you see as a comfortable purchase rate?
Vrieze and Jensen said 11 cents would be appropriate, while others mentioned a price of 16 cents would be more reasonable.
According to Crave, one large factor is the potentially very expensive interconnect cost to hook up to the utility’s power lines. That can range from $100,000 to well over $1 million and can impact what the rate of return must be. PD
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